Also noisy pubs and bars, because they provide an excellent environment for criminals to converse without people overhearing them.
And possibly the postal service, because criminals can use them to send messages, explosives, drugs and children to other criminals, without the police knowing the approximate contents of the communications.
It seems they want historical data so that they can run algorithms on large datasets and identify potential threats. In theory it's great as it will catch your average low level idealists, so rationally we can conclude that they're trying to focus on identifying, for example, potential IS recruits rather than organised crime.
joking aside, facial recognition has still some challenges, it can track a face wherever it goes but it's hard to assign a face to an identity unless it's constantly retrained (especially as people age/change)